Two Cases Of Patients With Acute Quadriplegic Myopathy

ObjectiveThe aim of this study was to improve our understanding of the clinical findings, laboratory investigation, and pathological changes of acute quadriplegic myopathy(AQM) and myofibrillar protein expression of AQM. Specific interest was focus on the effects of this disorder on sarcomeric proteins, i.e., myosin heavy chain(MyHC):actin ratio.Methods2cases of patients with AQM hospitalized during2008to2010were included in this study. Muscle biopsy samples were collected from vastus lateralis of two patients during the acute phase of AQM and observed by light microscope using enzyme-histochemical techniques. Semi-quantitative analyses of myosin and actin expression were determined by densitometry following sodium dodecyl sulfate-polyacrylamide gel electrophoresis of AQM myofibril specimens from two patients.ResultsTwo patients both had a medication history of antidepressants and antipsychotic drugs, followed by unexplained fever. After admission, they were provided with endotracheal intubation and mechanical ventilation. After intubation, all the patients emerged severe generalized flaccid muscle weakness or complete paralysis of limb and respiratory muscles, with tendon reflexes of extremities weakening, leading to the difficulty to wean from the mechanical ventilator. The patient showed intact cranial nerve innervated craniofacial muscles, and their sensory and cognitive functions remained normal. Serum creatine kinase in two patients increased by varying degrees during the acute phase. Myoglobin was not detected in the urine, hepatic and renal function was preserved. Two patients were given treatment such as anti-infection, maintain the electrolyte and acid-base balance, blood glucose control, nutritional support, prevention of complications and functional exercise, etc.. The condition of one patient improved and he gradually weaned from the ventilator after a few months; however, the condition of another patient deteriorated. He discharged from the hospital finally. Pathologically, quadriceps biopsies of2patients showed myogenic changes:the muscle fibers are of various sizes, atrophic fibers with unstained regions, with dominating type Ⅱ fiber atrophy; a small amount of necrosis and signs of muscle fiber regeneration were observed; irregular form and vacuolization were found, and there were no infiltration of inflammatory cells. The myosin heavy chain:actin ratios of the two patients were0.633and0.748respectively. These ratioes were significantly decreased during the acute stage of the disease compared with age-matched healthy controls (mean1.42).ConclusionsAcute Quadriplegic Myopathy is a specific acquired myopathy in critically ill patients in the intensive care unit (ICU). AQM is a rare clinical disease, but it’s common in the critically ill patients. Typically, AQM is recognized when ICU patients are slow to wean from the mechanical ventilator. Patients with AQM are characterized by severe flaccid muscle paralysis and muscle wasting of spinal nerve innervated limb and trunk muscles, with intact or less affected cranial nerve innervated craniofacial muscles, sensory and cognitive functions. The muscle weakness is associated with a preferential loss of the myosin and myosin-associated thick filament proteins, an in-excitable muscle membrane and muscle fiber atrophy. Other pathological features include low compound muscle action potentials and intact motor and sensory nerve conduction velocities. Prolonged mechanical ventilation, unloading of limb muscles and the administration of systemic corticosteroids or postsynaptic neuromuscular blocking agent, or in combination with an underlying systemic illness have been suggested as important triggering factors in AQM.This potentially lethal condition is associated with increased mortality, negative consequences for recovery from primary disease, drastically impaired quality of life and increased health care costs. The clinical manifestations of AQM are not specific, many clinicians don’t quite understand the disease and made a lot misdiagnosis which resulted in delays of patients’treatment. Therefore, in order to reduce misdiagnosis rate, clinicians should expand knowledge, raise the awareness of this disease and ensure early detection, early diagnosis and early treatment. Over the past decades, the treatment of critically ill patients has improved dramatically, resulting in a significantly better survival rate. While ICU outcome has traditionally focused simply on survival, modern critical care also addresses post-ICU complications and quality of life. Neuromuscular dysfunction, resulting in muscle wasting and weakness, is the most persistent and debilitating of problems for survivors after hospital discharge. To improve the quality of life in AQM survivors, therefore, there is, a significant need for more research focused on the mechanisms underlying the muscle wasting and weakness in AQM patients. A more complete understanding of the mechanisms underlying the preferential loss of the thick filament protein myosin is of significant interest in the design of intervention and prevention strategies.